1. Field of the Invention
The present invention relates to a throughflow cylinder for a throughflow drying unit, in particular for tissue.
2. Description of the Related Art
An example of a throughflow cylinder is recited in an article “Hightech Durchströmtrocknung für Tissue” (High-tech Throughflow Drying For Tissue) of Fleissner GmbH in ipw 3/2001, page 21.
The previously known throughflow cylinders, also called TADs (through air drying) cylinders, consist of metal. The tissue web is guided on a screen over the throughflow cylinder. A gaseous medium is pressed through the tissue web by way of the throughflow cylinder. This gaseous medium or fluid can have a temperature of more than 300° C. In the event of a web break, this temperature acts directly on the screen which is now no longer cooled by the tissue web. To avoid any damage to the screen as a consequence of the high temperature, the screen is cooled in a shock-like manner by way of a cold water jet tube. The throughflow cylinder is also exposed to this temperature shock, which results in extreme thermal stresses. Complex constructions are necessary to prevent the metal from tearing or to reduce the risk of tearing (see the article “Hightech Durchströmtrocknung für Tissue” (High-tech Throughflow Drying For Tissue) of Fleissner GmbH in ipw 3/2001, page 21).
What is needed in the art is an improved throughflow cylinder in which the previously named problems have been eliminated.